What Is a Countermovement Jump (CMJ) and What Does It Tell You?

Written By Scott Jablonka

In the world of sports performance and rehabilitation, one of the most valuable tests an athlete can perform is the Countermovement Jump (CMJ). While it may look like a simple vertical jump, modern force plate technology like VALD’s ForceDecks turns the CMJ into a powerful tool for measuring athletic performance, fatigue, asymmetries, and injury risk. In reality, it kicks back A TON of data to us that we need to interpret and use for our assessment and intervention.

At CMD, we use the CMJ testing to help our patients and athletes train smarter, recover more effectively, and objectively track progress over time. This isn’t just for the stereotypical “athlete.” This is for EVERYBODY. Everybody need to be able to generate force equally. So this even applies to little Estelle at the nursing home. She still has to get up from the dinner table.

What Is a Countermovement Jump (CMJ)?

A Countermovement Jump is a vertical jump that begins with a quick downward movement before explosively jumping upward.

The movement includes:

  • A rapid lowering phase (eccentric loading)

  • A transition phase (amortization)

  • An explosive upward drive (concentric force production)

Using force plates, we can analyze how the body produces and absorbs force during every phase of the jump. While the jump itself may only take a second, the data collected provides an in-depth look at how an athlete moves and performs.

Why Is CMJ Testing Important?

Traditional jump testing typically measures only jump height. However, force plate technology reveals how an athlete achieved that jump.

Two athletes may jump the same height but use completely different movement strategies.

CMJ testing can help identify:

  • Lower body power output

  • Explosiveness

  • Neuromuscular fatigue

  • Right-to-left asymmetries

  • Force absorption strategies

  • Compensation patterns

  • Readiness to train or compete

  • Return-to-play progress after injury

This makes CMJ testing valuable for:

  • Athletes

  • Rehab Patients 

  • Strength coaches

  • Sports performance professionals

  • Tactical athletes

  • Youth athletes

  • Post-surgical rehabilitation

  • Weekend Warriors

  • HYROX athletes

  • Nursing Home/ Retirement Home redisdents

What Does VALD ForceDecks Measure During a CMJ?

Using ForceDecks, we can capture hundreds of data points during a single jump. Some of the most important metrics include:

Jump Height

The most recognized metric, showing overall vertical displacement and explosive capability. This is usually what people like to see, especially the Big Man On Campus (BMOC) wanting the top spot on the leaderboard.

Peak Force

Measures the maximum force an athlete can generate during the jump. This is a true measurement of strength production and a metric we like to use to gauge progress with our strengthening programming.

Rate of Force Development (RFD)

How quickly force is produced.

F=ma

This is critical for sports requiring acceleration, sprinting, jumping, and rapid direction changes. The faster you can generate force, the more likely your opponents will be reading the back of your jersey.

Eccentric Deceleration

Evaluates how effectively the athlete controls the downward phase before exploding upward.

Poor eccentric control is commonly seen in:

  • ACL rehab

  • Knee pain

  • Tendon injuries

  • Fatigue states

Concentric Impulse

Measures the total force produced over time during the upward movement.

Asymmetry Scores

One of the most important features of force plate testing.

ForceDecks can identify differences between the right and left leg during:

  • Force production

  • Braking

  • Landing

  • Stability

Even subtle asymmetries may indicate:

  • Compensation patterns

  • Previous injury adaptations

  • Increased injury risk

  • Inefficient movement strategies

These measurements were historically “measured” through visual observation and subjective measures. Now we can put an exact number on them and track them along our process.

How CMJ Testing Helps Prevent Injuries

Athletes often compensate long before pain appears.

Force plate testing helps identify hidden movement inefficiencies that may not be visible during standard movement screens.

For example:

  • An athlete recovering from ankle sprains may offload one side during jump takeoff.

  • A baseball player with hip stiffness may show reduced force absorption.

  • A fatigued athlete may display slower force production despite normal jump height.

These findings allow coaches and clinicians to modify:

  • Training load

  • Recovery strategies

  • Strength programming

  • Plyometric progression

  • Return-to-sport timelines

CMJ Testing for Return-to-Play Decisions

One of the biggest mistakes in rehab is returning athletes to sport based solely on pain levels or time since injury. This is out-dated and frankly, negligent.

Objective data matters.

At Carolina Movement Doc, we use CMJ testing alongside:

  • Sprint testing

  • Strength testing

  • Mobility analysis

  • Change-of-direction testing

  • Movement assessment

This helps create a more complete picture of athletic readiness.

Force plate data is especially valuable following:

  • ACL reconstruction

  • Achilles injuries

  • Patellar tendon injuries

  • Hamstring strains

  • Stress fractures

  • Hip and knee surgeries

CMJ Testing for Baseball Athletes

For baseball players, explosive lower-body power directly impacts:

  • Sprint speed

  • Rotational power

  • Throwing velocity

  • Deceleration capacity

CMJ testing can reveal whether an athlete efficiently transfers force from the ground upward.

This is particularly important during:

  • Offseason training

  • Return-to-throwing programs

  • High-volume tournament schedules

  • Velocity development phases

What Happens During a ForceDecks Assessment?

A typical CMJ assessment at Carolina Movement is quick, safe, and highly informative.

Athletes perform several jumps on dual force plates while the system records detailed biomechanical data.

We commonly combine CMJ testing with:

  • Mid-thigh pull testing

  • Broad jump testing

  • 10-yard sprint testing

  • 5-10-5 agility testing

  • Upper and lower body strength testing

  • Mobility and range-of-motion analysis

The goal is not just to collect numbers — it’s to understand how the athlete moves and where performance limitations may exist.

Final Thoughts

The Countermovement Jump is far more than a vertical jump test. When paired with advanced force plate technology like ForceDecks, it becomes a window into athletic performance, fatigue management, injury prevention, and rehabilitation progress.

Whether you are a competitive athlete, recovering from injury, or simply looking to improve performance, CMJ testing provides objective data that helps guide smarter training decisions.

If you are interested in force plate testing, performance assessments, or return-to-play evaluation in the Gastonia area, Carolina Movement Doc can help you better understand how your body produces and absorbs force — and how to optimize it for long-term performance.

Get ahold of us today and let’s get started with tracking your progress an reducing your injury along the way.

Click here to get started —> CLICK HERE

Scott Jablonka
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How We Use VALD ForceDecks at Carolina Movement to Build Stronger Humans